WATER QUALITY CLASSIFICATION BASED ON WATER QUALITY INDEX IN SUNGAI LANGAT, SELANGOR, MALAYSIA

A study to determine the Water Quality Index (WQWQII) of Sungai Langat was conducted in which 10 sampling stations were selected. Water quality samples were taken according to the standard methods recommended by the American Public Health Association (APHA) and manual HATCH for the lab tests. The measurements done on site were to obtain reading parameters such as temperature, pH and dissolved oxygen (DO) levels using the meter YSI 556 MPS. Laboratory analysis was conducted to get parameter readings such as total suspended solids (TSS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and ammoniacal-nitrogen (NH3-N). All the parameters tested were the sub index needed in the calculation of the water quality classification. River classification is done according to the National Water Quality Index (WQS). The Pearson statistical correlation analysis was carried out to show the relationship between the sub-index parameter of (0.01) and the sampling stations for all parameters studied. Stations 1 and 2 were categorized in class I with an average value of (93.55 +/- 2.27) and (92.56 +/- 2.54) respectively. Station 3 recorded an average WQI reading of (91.55 +/- 2.33) in class II while stations 4 to 10 recorded readings from (76.03 +/- 4.72) to (68.60 +/- 4: 51) in class III. Generally the results show that the Water Quality Index from the sampling stations are categorized between classes to III.